Valves are devices for controlling the passage of fluid or air through a pipe, duct, sleeves, or other similar devices. Conventional valves utilize closing elements to interfere with fluid flow. A pinch valve is a control valve that uses a pinching effect to obstruct flow in an internal sleeve. Pinch valves differ from conventional valves because pinch valves apply pressure on a sleeve to prevent flow, instead of using separate closing elements.
Pinch valves do not need closing elements, so that the flow of fluid or air through the valve will be unimpeded by closing elements. Pinch valves are frequently used in applications where solid or semi-solid material, such as powder, granules, pellets, fibers or similar material, flow within the sleeve. Pinch valves can be used in soft applications, such as waste water plants or heavy industrial applications.
Since pinch valves have an unobstructed flow path in the open position, pinch valves can create minimal pressure drops to enhance downstream instrumentation control. The unobstructed flow through pinch valves can be advantageous in handling fluids that can shear when forced through complex internals. Pinch valves are highly tolerant of particulates in the fluid streams and can be very simple in construction.
Conventional pinch valves include mechanical pinch valves that can apply pressure using a movable closure bar at one point of a circumference of a sleeve. Such pinch valves can position the movable closure bar at the top of the circumference of the sleeve, so that the closure bar flattens the sleeve towards a fixed bottom to deform the sleeve, greatly.
Other pinch valves utilize air pressure to flatten the sleeve. Alternatively, mechanically driven presses are mostly screw-driven because high forces are needed to close pressurized sleeves and usually require fully encased sleeves.
Conventional pinch valves are primarily screw driven. Such pinch valves typically utilize elastomer sleeves with a pinch location in the centerline of the sleeve for wear purposes. The screw-driven linear gearing significantly reduces the mechanical efficiency, requires a substantial amount of power, and has an increased cost associated with the actuator-valve combination. The presence of a screw-driven system also requires multiple turns to drive the closure bars together which can effect closure times, adversely, and can lead to safety concerns in applications that require a fast shut-off. Therefore, there is a need for an improved pinch valve that meets requirements of a broad range of applications while providing ease of maintenance, reduce thrust required to close, fast maintenance, and less costly actuators.